The hero of this extraordinary documentary is the overweight, semi-alcoholic, publicity-seeking 54-year-old Martin Strel, professional gambler, flamenco teacher, environmentalist and national hero in his native Slovenia, who raised money for his expeditions by publicising McDonald's and a local delicacy called the horseburger. Having swum the length of the Danube, the Mississippi and the disgustingly polluted Yangtze, Strel decided in 2006 to swim the mighty Amazon from source to sea. Among the various hazards he faced was a small fish called the candiru that allegedly swims up the urethra as a preamble to devouring the penis.

The man is a mad obsessive and one is surprised that he hasn't ended up in the exotic trophy room of Werner Herzog, whose films Big River Man resembles. As if Strel were not enough, the expedition was accompanied as navigator by an American hippy, Matthew Mohlke, who makes Dennis Hopper's photographer in Apocalypse Now look like Al Gore and regards Strel as "almost Christ-like" and "the last superhero in the world." Strel's softly spoken young son brings a certain sobriety to the proceedings.